Cold weather prevents, or at least severely curtails, operation of outdoor equipment using diesel engines as the motivating power. As the ambient temperature drops below freezing, the diesel fuel thickens or jells, preventing a free flow of the fuel through the fuel system lines and prevents efficient operation of the engine. Most diesel fuel pumps are generally sufficiently powerful to pump the fuel even with extreme gelation, however, the fuel filter tends to retard and/or stop the flow, and the fuel jets of the engine tend to wear rapidly or plug under such extreme conditions. Gelation of the diesel fuel prevents the efficient flow of fuel through the injection jets of the cylinders and prevents optimum operation of the diesel engine.
Many attempts have been tried to solve the problem, but numerous factors have weighed against success of these previous attempts. Many such attempts involve changing the fuel system itself, adding units to the system which change fuel flow characteristics or introducing external agencies, such as electric heaters, for heating the incoming combustion air or the diesel fuel. Some attempts have been made to heat the fuel tank, while some have attempted to heat the fuel by insertion of heaters in the fuel line requiring a reconstruction of the fuel line. For example, in U.S. Pat. No. 3,209,816, issued Oct. 15, 1965, the existing fuel line of an engine is cut and a heater-separator is inserted into the fuel line. This requires cutting into the existing fuel lines, reconstructing the fuel system to accommodate an added heater-separator, and rearranging the system to include the added device under the hood for the engine. In U.S. Pat. No. 3,626,917, the fuel system is reconstructed to insert a self-contained heater which includes a combustion chamber separate from the engine and utilizing fuel from the diesel fuel tank to heat air for combustion in the engine. This system is primarily for starting the engine and has no effective utility for the engine after starting. U.S. Pat. No. 3,699,938 shows a way to replumb the fuel lines of a diesel engine which includes an engine coolant liquid heater for incoming fuel to the engine. This system, of course, requires that the engine be started and all the engine coolant heated before the air heater is effective in heating the incoming fuel. U.S. Pat. No. 3,630,183 includes an elaborate air pre-heater for a diesel engine using a separate fuel burner to heat the incoming air for the diesel fuel for the engine.
Thus, the prior art shows numerous attempts to aid cold weather operation, but these have only been partially successful at best. Many such systems introduce another element of risk into the operation of the diesel, i.e., separate burners, which only provides for heating air for the combustion of the engine.